Ignition timer



May 28, 1940. J. L. ARTHUR 2,202,077

IGNITION TIMER -Filed June 19, 1939 I INVENTOR BY @mm/ MM ATTORNEYI/ Patented May 1940 UNITED` sTATEs IGNITION TIMER James L. Arthur, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June `19, 1939, Serial No. 279,935

This invention relates to ignition timers for internal combustion ignition apparatus and more particularly to the type of apparatus in which the circuit breaker of the ignition timer is mounted upon a plate, called the circuit breaker plate which is adjustable rotatively about the axis oi the cam which operates the circuit breaker in order to vary the timing of the ignition.

One form of the particular circuit breaker referred to is disclosed in my Patent No. 2,187,070, granted Jan. 16, 1940. My said application discloses the mounting of the circuit breaker plate upon the outer race of the ball bearing, the inner race of which is pressed over avshait which supports the ignition timer cam. The timer housing provides a bearing for the outer race of the ball bearing. This construction provides for the mounting of the circuit breaker plate accurately so that the axis of the plate coincides precisely with the axis of rotation of the timer cam. This construction provides for rotation of the circuit breaker plate with very little frictional resistance so that the plate may readily be adjusted automatically by devices responsive to variations in 25 pressure in the engine fuel intake pipe.

Automotive ignition apparatus is usually of the one wire type, the return to the current source being thru a ground connection provided by the automobile frame to which the storage battery is 30 connected, the engine frame on which the metal ignition timer housing is mounted and by means of a flexible wire connecting the movable circuit breaker plate with the ignition timer housing. This flexible lead from the circuit breaker plate to the timer housing is adequate for carrying the direct current supplied by the current source to the ignition system. There are certain high frequency currents of relatively short duration which pass thru the ignition timer concurrently with the discharge of the secondary circuit oi.' the system to provide ignition sparks. These high frequency transient currents are not conducted readily by the flexible lead which provides the ground connection between the circuit breaker plate and the timer housing, because this lead,

when of a length sufcient to provide substantially no hindrance to rotation of the circuit breaker plate, oiIers appreciable resistance to the iiow of -the high frequency transient currents.

Therefore these transient currents of high frequency seek a path to ground thru the `ball bearing which supports the circuit breaker plate co axially with respect to' the timer cam. In time the balls of the ball bearing will be pitted by the high frequency transient currents. It is neces- (Cl. 20G-31) sary therefore to insulate the ball bearings from ground.

The object of the present invention is to provide for insulatingly mounting the circuit breaker plate upon the outer race of the ball bearing.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. 1 is a plan View of an ignition timer unit embodying the present invention, the distributor rotor and distributor cap being removed.

Fig. 2 is a sectional view taken substantially on the line 2-2 of Fig. 1.

Figs. 3 and 4 are sectional views taken on the line and reading in the directionof the arrows 3 3 and 4-4 respectively of Fig. 2.

The ignition timer housing includes a cup 20 enclosed by distributor cap 2| a fragment of which is shown in Fig. 2. The cup 20 provides a bearing 22 in which the outer race 23 of a ball bearing 25 is rotatively supported, said bearing 22 providing a clearance of about .001". Balls 24 support the outer race 23 upon the inner race 26 which is press fitted over a shaft 21 to which timer cam 28 is xed. Cam 28 operates one or more circuit breakers each comprising a lever 30 insulatingly mounted on a pivot stud 3| and provided with a non-conducting rubbing block 32 engaged by the lobes of the cam 28. A leaf spring 33 urges the rubbing block 32 toward the cam 28 and a contact 34 carried by the lever 30 toward a stationary contact 35 carried by a bracket 36. One end of the spring 33 is attached to the lever 30 and the other end of the terminal 31 which is insulatingly supported bythe bracket 36. The insulated terminals 31 of the two circuit breakers shown are wired together by a ilexible lead 38 and are connected by flexible lead 39 with a main terminal 40. )ne of the circuit breakers is mounted upon an upper plate 4I which is adjustably mounted upon the circuit breaker plate 42 upon which the other circuit breaker is directly mounted.

The outer race 23 of the ball bearing 25 is provided with an annular groove 50 which receives a resilient split washer 5| which provides a shoulder against which is positioned a non-conducting washer 52 having an inside diameter such as to snugly iit the bearing race 23 and having an outside diameter such as to snugly iit within a cylindrical recess 53 provided by an annular flange 54 provided by'plate 55. The annular flange 54 merges with a iiat circular ange 56 bearing against the under side of the non-conducting washer 52. The outer periphery of the plate 555 is shaped to provide an annularange 51 which bears against the under side of the circuit breaker plate 42. The plate 42 is located with respect to the plate 55 by three screws 58 the heads of which accurately iit into the countersunk holes or plate 42 and the threads of which are threaded into tapped holes in the plate 55. Between the upper end face of the ball bearing race 23 and the lower side oi' the plate 42 is located a non-conducting washer which is maintained concentrically with the axis of the shaft 2l' by three small boss es Bi formed by extruding portions of the plate 42. When the screws 58 are tightened the washer 80 is confined between the bearing race 23 and the bearing 42 and the non-conducting washer 52 is confined between the split washer or ring and the ilange 56 of the plate E5. The in side diameter of the plate 55 is substantially greater than the outside diameter oi the bearing race 23 so that there is no metal contact. The spacing between the metal parts such as 56 and 23 need not be very great because the high freI quency transient currents are capable of jumping only very minute gaps. While the insulating washers 52 and 60 are relatively thin and the spacing between the flange 56 of the plate 55 and adjacent the metallic parts is relatively smaii, the insulation is suiicient to raise the resistance to the ow of high frequency transient current to a value in excess of the resistance aorded by the ground lead 'l which connects the breaker plate d2 with the ignition timer cup it.

The timing of the ignition may be varied by rotating the circuit breaker plate ft2 either manu ally or by some automatic device such as a dem vice which is responsive to variations in pressure in the engine intake pipe. Fig. l shows a form or? such device. This device comprises a suction chamber 8@ connected by fitting di with the enm g'mel intake manifold and housing a diaphragm not shown connected by link 82 with the circuit breaker plate d2.

While the embodiment of the present invention @andere as herein disclosed, constitutes a preferred form, it is to be understood that other iorms might be adopted, al1 coming within the scope of the claims which follow.

What is claimed is as* follows:

l. In an ignition timer, the combination of a circuit breaker, a plate supporting the circuit breaker, a cam for operating the circuit breaker, a shaft carrying the cam, an anti-friction bearing having inner and outer races, the innerrace being mounted on said shaft, and means for insulatlngly supporting the circuit breaker plate upon the outer race.

2. In an ignition timer the combination of a circuit breaker, a plate supporting the circuit breaker, a cam for operating the circuit breaker, a shaft carrying the cam, an anti-friction bearing having inner and outer races, the inner race heing mounted on said shaft, a shoulder provided by the outer race, a nom-conducting washer tted around the outer race and bearing against said shoulder, insulating means spacing the circuit breaker plate from an e'nd of the outer race, and means for clamping the plate against said insulating means and said washer against said shoulder and for maintaining said plate concentric with said washer.

3. In an ignition timer, the combination of a circuit breaker, a plate supporting the circuit breaker, a cam for operating the circuit breaker, a shaft carrying the cam, an anti-friction bearing having inner and outer races, the inner race being mounted on said shaft, a shoulder provided by the outer race, a non-conducting washer iitted around the outer race and bearing against said shoulder, insulating means spacing the circuit breaker plate from an end of the outer race, a clamping plate providing a recess receiving the washer and a flange engaging the side of the washer remote from saidshoulder, and means for attaching the circuit breaker plate to the clamping plate, and cooperating therewith to cause the circuit breaker plate to be forced against said insulating means and said washer against said shoulder.

JAMES L. ARTHUR. 

